Writing boards such as whiteboards and blackboards are frequently used in many different settings (e.g., academic, corporate, non-profit, residential, etc.). Various content including text, drawings, tables, charts, and graphs may be drawn or placed on the writing boards for lectures, training, brainstorming sessions, etc.
In order to electronically memorialize these ideas, a photograph of the writing board may be taken. Further, image processing such as optical character recognition (OCR), stroke recognition, and reconstruction may be executed to extract the contents of the writing board from the image.
To recognize the content of a table handwritten on a writing board, the image processor or image processing software must locate the pixels that contribute to the “intent” of the table line along with various attributes of the table geometry, such as stroke width and line color. Once the cells of the table are identified, the content included in the cells (e.g., text) can be sent to a recognition module (e.g., OCR module).
However, some artifacts from the handwriting process and certain lighting conditions when the image of the writing board is taken may result in low quality input to the image processor. The low quality input can be seen when a mask of the input image is generated. For example, the writing board shown in FIG. 32 has at least three areas A1, A2, and A3 with irregularities. The area A1 shows a faded portion of a horizontal stroke of a marker or pen on the writing board caused by an intersecting vertical stroke. The area A2 shows where the marker itself faded during the stroke. The area A3 shows fading in the middle of the stroke. These irregularities can be captured in a mask (A1′, A2′, and A3′) as shown in FIG. 33. Other irregularities may also be found in the mask, such as a non-straight line, lines that curve at one end, finger smudges that erase parts of a line, marks made with a low-ink or dried up marker, and faded marks from a previous drawing that show up on the current image.
To recognize the geometry of the hand-drawn table on the writing board, such irregularities found in the mask should be considered, and the pixels that contribute to the intent of the line should be identified properly and precisely.